For a visualization of three-dimensional vector field on a two-dimensional plane, many attempts have been made since ancient times.
Most typically, there has been known a method of converting two components into coordinate values, and plotting an intersection thereof on a two-dimensional plane, providing each intersection with a note of attribute of the remaining third component (e.g. a town guide map), which however is unable to afford an easy gasp of a difference of the third component.
In this respect, there has been made also a graphic expression of an attributive feature of the third component (e.g. a town street guide map), which is still bound to the localization of information, and has covered successive changes in the attribute.
To this point, there has been generally employed a method of entering a continuous feature of two components (e.g. an outline such as of a coast, river, lake, or marsh) and attribute isopleth lines of the third component (e.g. contour lines), which is yet difficult of the intuitive visible perception of an attribute variation.
A topographic map is now supposed for more specific discussion.
In a mesh measurement by an analyzing mapper, the terrain is lattice-like divided, having altitude values given thereto, to provide a DEM (Digital Elevation Model) data. This is processed in a computer for calculation of parameters concerning, e.g, the terrain's heights, inclination angles, slope azimuths, laplacians, valley divisions, water systems, etc., allowing for a distribution of calculation results over a plane to be converted into a corresponding image.
In an airborne laser measurement, available data contain more detail information.
All the data is not involved in a topographic map.
For example, information on the height and inclination is extracted, to be entered as contour lines in the map. It however is uneasy to imagine a stereoscopic terrain therefrom.
There is also an image provided with a stereoscopic appearance, as a hill shade lighted from a diagonal upside, which has an emphasized inclination in a particular direction.
In this concern, there is a gray scale (tone of brightness) or a rainbow color (tone of hue) indicated in a terrain image, which allows an intuitive visual perception of terrain's geometrical features and their distribution, and is useful, but unable to give an effective visually solid appearance.
Reference-1: “Japanese Patent Application Laying-Open Publication 1-46902”
There is also an image processed by using either an aboveground opening or an underground opening as a mega filter, which allows a capture of terrain's features in a relatively large district, but feels something missing in visually solid appearance, particularly in local appearances to be visually solid.
Reference-2: “Iwate University thesis: Indication of terrain features by an opening, the photogrammetry and remote sensing, by Ryuuzou Yokoyama, Michio Shirasawa, and Yutaka Kikuchi (1999), vo. 38, no. 4, 26-34”.
Description is now made of conventional methods of providing a topographic map with a visually solid appearance.
(Stereo-Matching Image, Three-Dimensional Image)
Basically, an image that makes use of a parallax, employing two photographs. There are varieties of methods, such as cases by a red/blue filter, a polarizing filter, a diffraction grating, or a lenticurar lenz, any of which however has to be seen in a particular direction, and needs a glass. Moreover, expansion as well as scaling down is difficult.
The three-dimensional image is an image looked down in a particular direction, which is inadequate to read, as having a portion unseen if in shadow, looking small if distant, and lacking resolution if close. Moreover, time is necessary for image creation.
(Indication by Contour Lines)
The contour line is suitable to the indication of terrain in mountainous districts, but for steep inclinations (e.g. a sudden cliff part) or gentle slopes or flat lands (a plain part), the reading of topographic features takes a time due to an extreme convergence or divergence of contour lines having stepwise allotted heights.
The angle of inclination as well as the orientation is to be guessed from the variation of spacing between contour lines. Hence, being unfit in a simple expansion or scaling, it needs a remake in some case.
Crowded contour lines have their gaps lost, and are substituted by a legend of cliff. This task is complex, and constitutes an impediment to vectorization.
Small irregularity cannot be read unless a height is given to each contour line.
(Set of Image Data Having Two-Dimensional Altitude Values)
In a mapping work by aerial photographic measurement, the acquisition of information is directly made of contour lines as connected particular altitudes, having no altitudes given between contour lines.
In the case of mesh measurement by an analyzing mapper or airborne laser measurement, the DEM data is acquired, and based thereon a two-dimensional distribution of contour lines is determined, whereby, although contour lines are smoothed as necessary, information else than finally contained in contour lines, e.g. information of a three-dimensional geometry between contour lines, is left unused.
This invention was made in view of the foregoing points.
It therefore is an object of the invention to provide a visualization processing system, a visualization processing method, and a visualization processing program, which are adapted to visualize a vector field, with local solid attributes thereof inclusive, on a substantially two-dimensional field of view, in a manner that allows an intuitive visible perception.
It also is an object of the invention to provide a visualization processing system, a visualization processing method, and a visualization processing program, which are adapted to generate a gradient reddening stereoscopic image that allows at a glance a stereoscopic grasp of terrain's heights and inclination degrees.